1. Field
The present disclosure relates generally to electromagnetic beams and, in particular, to modifying the wavefront of an electromagnetic beam. Still more particularly, the present disclosure relates to using or modifying the index of refraction of a metamaterial structure for the purposes of modifying the wavefront of an electromagnetic beam to within selected characteristics, properties, and tolerances.
2. Background
Electromagnetic radiation is often times used in communications. Typically, the electromagnetic radiation is transmitted and received in the form of electromagnetic waves. These waves may be transmitted and/or received in the form of an electromagnetic beam. In some cases, the electromagnetic beam may be transmitted in a manner such that the beam has Gaussian properties. For example, the electromagnetic beam may have a wavefront with a Gaussian intensity profile. This type of electromagnetic beam may be referred to as a Gaussian beam.
Gaussian beams are prone to diffraction. Diffraction occurs once the waves that form an electromagnetic beam propagate and may be increased when the waves encounter an obstacle. When the waves encounter the obstacle, the waves may bend around the obstacle. The bending of the waves may alter the amplitude and/or phase of the waves. In some cases, the diffraction of a beam may result in a loss of information that is carried within the electromagnetic beam. More specifically, the diffraction may result in a loss of power of the electromagnetic beam at a target, which may, in turn result in a reduction in signal to noise ratio.
True Bessel beams, however, are non-diffractive. In other words, a true Bessel beam does not diffract as the waves that form the beam propagate through one or more media. A Bessel beam may be an electromagnetic beam having a wavefront with a Bessel intensity profile. Currently, engineering a true Bessel beam may not be possible. However, approximations of a Bessel beam may be engineered.
Currently, axicon lenses may be used to change Gaussian beams into Bessel beams. An axicon lens is a lens that has a conical surface. An axicon images a point source into a line along the optic axis, or transforms a beam into a ring. However, some currently available axicon lenses may be able only to change Gaussian beams comprised of light waves into Bessel beams. These axicon lenses may not be configured for use with radio frequency waves.
Further, the geometry of an axicon lens may prevent the axicon lens from being integrated as part of an integrated optical system. For example, the size and/or shape of the axicon lens may prevent the axicon lens from being integrated into an integrated optical system. Therefore, it would be desirable to have a method and apparatus that takes into account at least some of the issues discussed above, as well as other possible issues.